Grass trimmers are a kind of gardening tools, which are used to trim the lawn. The grass trimmer includes a trimming head. The trimming head rotates at high speed to drive a cutting line mounted thereon to rotate so as to realize the cutting function.
The trimming head includes a spool allowing the cutting line to wind thereon. During the cutting operation, the cutting line is worn away gradually due to wear. After operating for a period, it is needed to change a new cutting line and wind the new cutting line around the spool. For the currently known cutting line, a user needs to rotate the spool manually to wind the cutting line around the spool. The winding operation is inconvenient and the winding speed is slow.